1. Field of the Invention
The present invention relates generally to staplers which are used to bind documents, and more particularly to an improved stapler and related method of operating the improved stapler in which a selective one of a plurality of different size staples all stored within the stapler itself is selected for dispensing without necessitating the removal of any staples of a non-selected size from the stapler, or reloading the stapler with the selected size of staples.
One of the most common devices which is found in offices all over the world is the stapler. Staplers have been used for years to fasten a plurality of sheets of paper together using a thin, U-shaped piece of wire which is known as a staple. The base of the U is known as the crown of the staple, with the legs of the U forming the staple legs. A plurality of sheets of paper to be fastened together is placed on top of anvil having recesses disposed in the top side thereof, which recesses function as a clinching device.
A cassette designed to hold a plurality of staples therein is disposed with the plurality of staples biased toward an end of the cassette which is located over the anvil. The cassette supports the plurality of staples on the bottom side of the crowns of the staples, with a single staple extending into a slotted aperture located in the end of the cassette which is located over the anvil, with the slotted aperture being aligned with the recesses in the anvil. The staple extending into the slotted aperture in the end of the cassette is unsupported on the bottom side of its crown.
A driving member, which is typically a thin driving blade, extends into the slotted aperture from the top of the cassette, above the staple extending into the slotted aperture in the end of the cassette. The driving blade is driven into contact with the top side of the crown of the staple extending into the slotted aperture in the end of the cassette, driving the staple legs into and through the plurality of sheets of paper on the anvil, and then into contact with the recesses disposed in the top side of the anvil. When the staple legs extend into the recesses in the anvil, they are clinched, typically towards each other, to thereby retain the staple in the plurality of sheets of paper to keep the plurality of sheets of paper together.
The driving blade is driven by hand in simple desktop staplers, with a single swift impact from the user's hand being more than sufficient to drive the staple into the sheets of paper and to clinch it on the bottom of the paper. In a slightly more sophisticated desktop stapler, the impact is provided electromechanically, with the sheets of paper being inserted into place to electrically trigger operation of the driving blade. In heavy duty industrial applications, a stapler may even be operated using pneumatic pressure to operate the driving blade.
All of these devices have one thing in common--the use of a cassette containing a row of staples of a particular size. This leads to an observation which is both illustrative of the intrinsic operation of such staplers, and which is also an inherent disadvantage of such staplers. At any given time, they are designed to drive a staple of one particular size only, with that size staple being best applied to use to fasten together a specific range of numbers of sheets of paper.
For example, a short (one-quarter inch, for example) staple may be used to fasten from two to twenty-five sheets of paper together. If a greater number of sheets of paper are to be fastened together using a short staple, they will not be fastened together securely. Similarly, a long (three-quarter inch, for example) staple may be used to fasten from fifty to one hundred sheets of paper together. If a smaller number of sheets of paper are to be fastened together using a long staple, the staple legs will be over-clinched and may extend out in an unsafe manner, with the sheets of paper being held together relatively loosely.
As one might imagine, the art has addressed this problem in several ways, which can be divided into two types of staplers. The first type of stapler involves the modification of the cassette of the stapler so that it will accept staples of different lengths. The second type of stapler does not use staples of a fixed size, but instead makes staples from a continuous length of wire to fit the particular application.
An example of the first type of stapler is illustrated in U.S. Pat. No. 4,763,824, to Ebihara. The Ebihara reference discloses a stapler cassette which is capable of holding staples having a common width crown, but with different length staple legs. The Ebihara stapler is accordingly usable with staples of different lengths, but the staple supply in the cassette must be changed in order to change the length of staples which will be dispensed by the device. This is not particularly convenient, since the Ebihara device does not provide storage for staples other than the particular size staples loaded into the cassette.
Examples of the second type of stapler are illustrated in U.S. Pat. No. 4,318,555, to Adamski et al.; in U.S. Pat. No. 4,421,264, to Arter et al.; in U.S. Pat. No. 4,356,947, to Marshall, et al.; in U.S. Pat. No. 4,389,011, to Lovibond; and in U.S. Pat. No. 5,018,656, to Phelps. These devices all have two things in common--they use a continuous supply of wire from which variable lengths are cut to form staples having variable length staple legs, and they are all for use in copy machines. These staplers all solve the problem addressed by the present invention in that the handling and changing of different size staples is eliminated. However, these devices are all large, complex, and expensive, and they are not suitable for use in a desktop application.
It is accordingly the primary objective of the present invention that it provide a stapler which is capable of selectively dispensing a plurality of different staple sizes without requiring staples of different sizes to be unloaded from the stapler, or loaded into the stapler. It is also an objective of the present invention that it be capable of dispensing a wide range of different staple sizes, thereby eliminating the requirement that an office have multiple different staplers for different stapling applications. It is a related objective that a plurality of different size staples be storable in distinct locations in the stapler of the present invention, and that these distinct locations be independently accessible to allow the particular size of staples accommodated therein to be conveniently reloaded.
An additional objective is that the particular size of staples to be dispensed be selectable from among the plurality of sizes of staples stored in the stapler of the present invention in a simple and easy to accomplish manner. It is a further objective that the driving force used to operate the stapler of the present invention may alternately be the hand of a user, or an electromechanically driven mechanism. It is yet another objective of the stapler of the present invention that it be as compact as is possible, to thereby present a device which will have excellent application on a desktop where space is at a premium, or in other similar locations.
The stapler of the present invention must be of fabrication which is both durable and long lasting, and it should require little or no maintenance to be provided by its user throughout its operating lifetime. In order to enhance the market appeal of the stapler of the present invention, it should also be of inexpensive construction to thereby afford it the broadest possible market. Finally, it is also an objective that all of the aforesaid advantages and objectives of the stapler of the present invention be achieved without incurring any substantial relative disadvantage.